The invention relates generally to semiconductor devices, and more particularly, to an apparatus and method for forming a device such as a spherical-shaped semiconductor crystal.
Conventional integrated circuits, or "chips," are formed from a flat surface semiconductor wafer. The semiconductor wafer is first manufactured in a semiconductor material manufacturing facility and is then provided to a fabrication facility. At the latter facility, several layers are processed onto the semiconductor wafer surface. Once completed, the wafer is then cut into one or more chips and assembled into packages. Although the processed chip includes several layers fabricated thereon, the chip still remains relatively flat.
Manufacturing the wafers requires creating rod-form polycrystalline semiconductor material; precisely cutting ingots from the semiconductor rods; cleaning and drying the cut ingots; manufacturing a large single crystal from the ingots by melting them in a quartz crucible; grinding, etching, and cleaning the surface of the crystal; cutting, lapping and polishing wafers from the crystal; and heat processing the wafers. Moreover, the wafers produced by the above process typically have many defects. These defects can be attributed to the difficulty in making a single, highly pure crystal due to the cutting, grinding and cleaning processes as well as impurities associated with containers used in forming the crystals. These defects become more and more prevalent as the integrated circuits formed on these wafers contain smaller and smaller dimensions.
In co-pending U.S. patent application Ser. No. 08/858,004 filed on May 16, 1997, a method and apparatus for manufacturing spherical-shaped semiconductor integrated circuit devices is disclosed. Although certain manufacturing methods for making spherical shaped crystals are disclosed in the above-referenced application, an improved method of making the spherical shaped crystals, which includes fewer defects and is more manufacturable, is desired.